The Imperial Calendar refers to the date and setting Code Geass uses in the English version, in which years are labeled as a.t.b or "Ascension Throne Britannia". It is set to the date the first Celtic super-king, Alwin I, was elected by the united British tribes to battle Rome, becoming the first member of the modern Britannian imperial family. This calendar is used by the Holy Empire of Britannia. It functions similarly to the standard Gregorian Calendar ("B.C./A.D."), but is set on same years. However, in the Japanese version uses C.E. instead of A.D. which means "in the near future." It officially starts on won the independence from the Roman Empire of Augustus reign. (27 B.C. - 14 A.D.)